Residue behavior and risk assessment of pyraclostrobin and tebuconazole in peppers under different growing conditions

This study evaluates the residue behavior and risks of pyraclostrobin and tebuconazole in peppers. An analytical method for the simultaneous determination of the concentration of these fungicides in peppers was developed using ultra-high performance liquid chromatography-triple quadrupole mass spectrometry. Pepper samples were extracted with acetonitrile and cleaned with primary secondary amine and graphitized carbon black. The average recoveries of pyraclostrobin and tebuconazole under three fortification levels were 86.7-101.4% and 81.7-104.4%, with relative standard deviations of 4.0-7.2% and 3.8-10.9%, respectively. The limit of quantification of both fungicides in peppers was 0.01 mg/kg. The terminal residue trial of 30% pyraclostrobin and tebuconazole suspension concentrate was investigated for samples cultivated in open fields and greenhouses. The results showed that the terminal residues of pyraclostrobin and tebuconazole in peppers were lower than the maximum residue limits established by GB 2763-2021 (0.5 mg/kg for pyraclostrobin and 2 mg/kg for tebuconazole). The results of a statistical t-test indicated that there was no significant difference between samples grown in open fields and greenhouses. According to the international estimate of short-term intake (IESTI) calculation model, provided by the Joint FAO/WHO Meeting on Pesticide Residues, the acute dietary exposure risk of both fungicides in peppers was acceptable for the general population, with an IESTI of 0-3% and 0-5% of the acute reference dose for pyraclostrobin and tebuconazole, respectively.

Dissipation and dietary exposure risk assessment of pyraclostrobin, fluxapyroxad, difenoconazole, and azoxystrobin in the Fritillaria field ecosystem

Fritillaria (Beimu in Chinese) is a well-known traditional Chinese medicinal herbal and valuable health food, which has attracted more and more attention. In this study, an efficient method was developed to determine pyraclostrobin, fluxapyroxad, difenoconazole, and azoxystrobin in plants, fresh Fritillaria, dry Fritillaria, and soil via liquid chromatography-tandem mass spectrometry. The average recoveries of the method were 78.9-109.7% with relative standard deviations of 0.94-11.1%. The dissipation half-lives of the four fungicides were 4.4-7.7 days in the Fritillaria plant and 11.6-18.2 days in the soil. The terminal residues of four fungicides were 0.033-0.13 mg/kg in fresh Fritillaria, 0.096-0.42 mg/kg in dry Fritillaria, and 0.12-0.74 mg/kg in soil. In the risk assessment of dietary exposure, all the chronic hazard quotient and acute hazard quotient index values were far below 100%, which were both acceptable to consumers. Accordingly, 7 days was recommended as the pre-harvest interval for the four fungicides in Fritillaria. This work could guide the safe use of these fungicides in Fritillaria and also give a reference for the Chinese government to establish the maximum residue limits (MRLs).

Evaluation of acetamiprid and azoxystrobin residues and their hormonal disrupting effects on male rats using liquid chromatography-tandem mass spectrometry

Endocrine-disrupting compounds as pesticides affect the hormonal balance, and this can result in several diseases. Therefore, the analysis of representative hormones with acetamiprid (AC) and azoxystrobin (AZ) was a good strategy for the investigation of the endocrine-disrupting activity of pesticides. Hence, a sensitive and rapid analytical method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. The method was validated for the analysis of AC, AZ, estriol, estrone, progesterone, and testosterone in the serum, testis, and liver of rats. The correlation between the residues of pesticides and the disturbance of the endocrine system was evaluated. The different mass parameters, mobile phase types, analytical columns, injection volumes, and extraction solvents were compared to get the lowest limit of detection of the studied compounds. The detection limits of AC, AZ, estriol, estrone, progesterone, and testosterone were 0.05, 0.05, 1.0, 10, and 1.0 ng/ml, respectively. The method developed was applied to evaluate the changes in these hormones induced by the duration of exposure to AC and AZ in rat testis and serum. The hormones level in rat serum and testis had a significant decrease as they were oral gavage treated with different high concentrations of studied pesticides. Both pesticides were distributed in the body of rats by the multi-compartment model (liver, testis, and serum).

Terminal residue and dietary intake risk assessment of prothioconazole-desthio and fluoxastrobin in wheat field ecosystem

BACKGROUND

Wheat is one of the most important cereal crops worldwide, and use of fungicides is an essential part of wheat production. Both prothioconazole and fluoxastrobin give excellent control of important seed and soilborne pathogens. The combination of these two fungicides shows a complementary mode of action and has a wide usage around the world. But the residue levels of these fungicides in the wheat matrix are still unknown.

RESULTS

In the current study, a simple, low-cost and highly sensitive method using modified QuECHERS procedure combined with high-performance liquid chromatography-tandem mass spectrometry was developed to simultaneously quantify E- and Z-fluoxastrobin and the main metabolite prothioconazole-desthio of prothioconazole in the wheat matrix. The recoveries of prothioconazole-desthio, E-fluoxastrobin and Z-fluoxastrobin ranged from 84% to 101%, with relative standard deviation of less than 13.2%. The terminal residues of prothioconazole-desthio and E- and Z-fluoxastrobin were studied in wheat grain and straw under field conditions. The results showed that the terminal residue of the target compounds ranged from <0.01 to 0.029 mg kg^-1 and <0.05 to 7.6 mg kg^-1 in wheat grain and straw (expressed as dry weight), respectively. The risk quotients of prothioconazole-desthio and fluoxastrobin were 0.2% and 3.2%.

CONCLUSIONS

The residue levels of the target analytes in wheat grain were lower than the maximum residue limits recommended by the Chinese Ministry of Agriculture. And the calculated risk quotient values were far below 100%, indicating a low dietary intake health risk to consumers. © 2021 Society of Chemical Industry.

Determination of azoxystrobin, topramezone, acetamiprid, fluometuron and folpet in their commercially available pesticide formulations by liquid chromatography

A rapid, simple, precise and accurate high performance liquid chromatographic (HPLC) analytical method was developed and validated for the determination of the active substances (a.s.) azoxystrobin, topramezone, acetamiprid, fluometuron and folpet in their respective commercially available formulations. The method was used for the analysis of samples under the frame of the national quality control program of plant protection products in the Greek market. Chromatographic separation of the active substances from additives and co-formulants is achieved using isocratic elution with acetonitrile and 0.1% phosphoric acid solution (60:40 v/v) at a flow rate of 0.4 mL min^-1 on a C₁₈ monolithic column (Chromolith Performance-RP18e 100 × 4.6 mm) and UV detection at 230 nm. Validation parameters of the method fulfilled acceptability criteria. Recovery of all individual compounds was in the range 97.8-100.9%. Precision expressed as relative standard deviation was lower than the theoretical values of the modified Horwitz equation. Correlation coefficients of linearity of response were better than 0.999. The benefits of the proposed method are significant reduction in analysis time and total cost since all analytes were determined with the same extraction procedures and chromatographic system. Analysis of real samples for all active ingredients confirmed fitness for purpose of the suggested method.

Study on stereoselective bioactivity, acute toxicity, and degradation in cucurbits and soil of chiral fungicide famoxadone

The chiral pesticide famoxadone is mainly applied to control fungal diseases on fruiting vegetables. The fungicidal activity, ecotoxicological effects, and degradation behavior of famoxadone enantiomers are less well known. In this study, a systemic assessment of the stereoselectivity of famoxadone was performed in cucurbits and soil. Famoxadone enantiomers presented distinct inhibitory activities among different fungal species. The bioactivities of R-(-)-famoxadone were 2.7-178 times higher than S-(+)-famoxadone toward five phytopathogens. Based on the obtained LC₅₀ values, famoxadone was super toxic to Eisenia foetida (E. foetida). Moreover, the acute toxicity of R-(-)-famoxadone presented 167 times greater to E. foetida than that of S-(+)-famoxadone, indicating that R-(-)-famoxadone showed higher bioactivity toward target organisms and non-target organisms than S-(+)-famoxadone. In addition, a simple high-performance liquid chromatography (HPLC) method was established to determine the stereoselective degradation of famoxadone in two species of cucurbits (cucumber and chieh-qua) and in field soil. The half-life values of famoxadone degradation were from 5.4 to 14.1 days, indicating that famoxadone was easily degraded. Additionally, no stereoselective degradation was found in cucurbits and soil. The results may provide promising implications for comprehensive environmental and ecological risk assessments of famoxadone.

Dissipation kinetics and safety evaluation of pyraclostrobin and its desmethoxy metabolite BF 500-3 in a cucumber greenhouse agroecosystem

Pyraclostrobin (PYR), a fungicide of the strobilurin class, is used to control many different kinds of fungal diseases in greenhouses and on agricultural fields. In the present study, an efficient method was established for simultaneously determining PYR and its metabolite BF 500-3 in cucumber fruits, leaves, and soil matrices using QuEChERS pretreatment coupled with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The residue levels and dissipation kinetics of PYR were determined under greenhouse conditions. The recoveries ranged from 89.8 to 103.6% with relative standard deviations (RSDs) of 3.6-7.5% at three spiking levels. The results demonstrated that PYR dissipated quickly in the cucumber field with half-lives (DT₅₀) of 2.14-4.17 days on different sites and in different matrices. The residue of its metabolite BF 500-3 was very low and showed a trend of first increasing and then decreasing. The degradation rate of PYR in soil was the fastest, followed by that on cucumber fruits and leaves. The terminal residue of PYR at an application rate of 150 g a.i. ha^-1 (the maximum recommended rate) in cucumber fruits was below the maximum residue limit (MRL) of 0.5 mg/kg established in China. However, the application of the fungicide at 225 g a.i. ha^-1 (1.5× the maximum recommended rate) resulted in residues that were above the MRL 1 day after the final application, which is an unacceptable risk. Therefore, the application dosage of PYR at the recommended rates was safe to human beings and animals.

Distribution of organochlorine, organophosphates, carbamate, thiocarbamate, pyrethroids, and strobilurins in surface sediments of the Rio de Ondas watershed by GC-MS

The determination of some pesticides in surface sediments can provide important information about their distribution in the water column. This work aimed to determine the distribution of the classes of pesticides along the Ondas River's hydrographic basin (ORHB), in eighteen different points, during the dry and rainy periods. The pesticides were extracted from the sediment samples by solid-liquid extraction and then analyzed using a gas chromatograph coupled to mass spectrometry. After the development and validation of the method, nineteen pesticides from the group of organochlorine, organophosphates, carbamate and thiocarbamate, pyrethroids, and strobilurins were quantified in at least one point in the two collection periods, with accuracy varying between 86 and 126%. The average concentrations were 0.020 ng g^-1 (carbofuran) to 249.123 ng g^-1 (dimethoate) and 0.029 ng g^-1 (carbofuran and sulfotep) to 533.522 ng g^-1 in the dry and rainy periods, respectively. The results showed a wide distribution of pesticide residues in the ORHB, with higher levels for dimethoate, phenitrothion, and malathion, which may be related to their agricultural use in the region. In Brazil, it does not have specific legislation for maximum permitted values of pesticides in sediment, allowing for inappropriate or prohibited use and, consequently, affecting water quality.

Evaluation of hematological parameters, oxidative stress and DNA damage in the cichlid Australoheros facetus exposed to the fungicide azoxystrobin

Azoxystrobin (AZX) is a broad-spectrum systemic fungicide massively used worldwide. Its mode of action consists in the inhibition of mitochondrial respiration decreasing the synthesis of ATP and leading to oxidative stress in the target fungus. However, whether this effect occurs in non target organisms has been scarcely studied. The objectives of this work were (1) to evaluate biomarkers of oxidative stress, hematological, physiological and of genotoxicity in the native cichlid fish Australoheros facetus exposed to environmentally relevant concentrations of AZX and (2) to compare these biomarkers in different developmental stages using juvenile and adult fish (n = 6) exposed during 48 h. The exposure concentrations were 0 (negative control, C (-)), 0.05, 0.5, 5 and 50 μg/L AZX of the commercial formulation AMISTAR®. Blood was drawn to evaluate hematology, and DNA damage through the comet assay (CA) and micronucleus test (MN). Genotoxicity was observed by mean of both biomarkers in juvenile and adult fish at 50 μg/L AZX. Samples of liver and gills were used to determine antioxidant enzymes activity, hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) contents. In juvenile fish inhibition of superoxide dismutase (SOD) was observed in liver at 0.05, 5 and 50 μg/L AZX and in gills at 5 and 50 μg/L AZX. Glutathione- S- transferases (GST) activity increased in gills at all AZX concentrations tested. In adult fish, increase of hepatic catalase (CAT) activity at 0.5 and 50 μg/L AZX and MDA content at 50 μg/L AZX were observed. In gills only H₂O₂ content showed changes at 50 μg/L AZX. The sensitivity showed by gills constitutes the first report about AZX toxicity in this organ. All these negative effects were observed in the range of realistic AZX concentrations, which warns of the possible consequences that it may have on the health of aquatic biota. Differences between juvenile and adult fish demonstrate the relevance of considering the developmental stage on the evaluation of biomarkers.

Fate, residues and dietary risk assessment of the fungicides epoxiconazole and pyraclostrobin in wheat in twelve different regions, China

The fungicides epoxiconazole and pyraclostrobin have been widely used to control wheat fusarium head blight. This study was designed to investigate the dissipation behaviors in different climate regions and provide data for the modification of maximum residue limits of the two fungicides. Wheat samples were collected from field sites in twelve different regions, China and analyzed with an HPLC-MS/MS method for simultaneous detection of epoxiconazole and pyraclostrobin in wheat. The average recoveries of epoxiconazole and pyraclostrobin in wheat matrix were 87-112% and 85-102%, respectively, with the relative standard deviations ≤8.1%. The limits of quantification of epoxiconazole and pyraclostrobin in grain and straw were both 0.01 mg/kg. The dissipations of epoxiconazole and pyraclostrobin followed first-order kinetics, with the half-lives of 10.3 days and 7.6 days, respectively. The terminal residues of epoxiconazole and pyraclostrobin in grain were below 0.034 and 0.028 mg/kg, separately, both lower than the maximum residue limits recommended by China. Based on Chinese dietary pattern and terminal residue distributions, the risk quotients of epoxiconazole and pyraclostrobin were 13.9% and 65.9%, respectively, revealing the evaluated wheat exhibited an acceptably low dietary risk to consumers.

Determination of pyraclostrobin dynamic residual distribution in tilapia tissues by UPLC-MS/MS under acute toxicity conditions

As a lipophilic fungicide, pyraclostrobin is highly toxic to aquatic organisms, especially to fish. In recent years, research has mainly focused on the pyraclostrobin residue in fish tissues under chronic toxicity, but less is known about its distribution in fish tissues under acute toxicity conditions. In this study, the distribution of pyraclostrobin in fish tissues (blood, liver, muscle and gill) was determined by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The purification effects of different purification materials [1) mixtures of PSA, C₁₈ and MgSO₄; 2) QuEChERS-PC; and 3) Oasis HLB SPE] were compared for the detection of pyraclostrobin in fish tissues. Finally, the quick and easy clean-up tool of the Oasis HLB SPE procedure was selected. Under optimum conditions, the linearities had a good relationship (determination coefficient R² > 0.999). The mean recoveries of the analyte for all tested concentrations ranged from 86.94% to 108.81% with RSDs of 0.7%-4.9%. The pyraclostrobin residue amount was much different in fish tissues. Furthermore, the pyraclostrobin residue in different fish tissues increased initially and then decreased gradually. The concentrations in each tissue were initially ranked before 120 min in the following order: gill > liver > blood > muscle. These phenomena may be attributed to the stress response of fish under acute poisoning. This is the first study to document the distribution of pyraclostrobin in fish tissues under acute toxicity conditions, and it provides reference for the management of agrochemicals in terms of aquatic ecological risks.

Determination of azoxystrobin and its impurity in pesticide formulations by liquid chromatography

A method was developed for the simultaneous qualitative and quantitative determination of azoxystrobin and its relevant impurity (Z)-azoxystrobin using high performance liquid chromatography with diode array detector (HPLC-DAD) in suspension concentrate (SC) pesticide formulations, with the aim of the product quality control. Method validation was realized according to SANCO/3030/99 rev. 5. The proposed method was characterized by acceptable accuracy and precision. The repeatability expressed as ratio standard deviation (%RSD) to relative standard deviation (%RSDr) was lower than 1, whereas individual recoveries were in the range of 97-103% and 90-110% for azoxystrobin and (Z)-azoxystrobin, respectively. The limit of quantification (LOQ) for the impurity ((Z)-azoxystrobin) amounted to 0.3 µg mL^-1 and was acceptable because it was lower than the maximum permitted level according to Commission Implementing Regulation (EU) No 703/2011 of 20 July 2011 for the active substance (azoxystrobin) being 25 g kg^-1 of the azoxystrobin content found. The method described in this paper is simple, precise, accurate and selective as well as represents a new and reliable way of simultaneous determination of azoxystrobin and its relevant impurity in formulated products.

Linear and Nonlinear Isotherm Models and Error Analysis for the Sorption of Kresoxim-Methyl in Agricultural Soils of India

Kresoxim methyl sorption in soils of five agro-climatic zones of India varied from 41.6% to 84.7%. Highest sorption was recorded in organic carbon rich Almora soil. Isotherm parameters for linear and non-linear Freundlich and Temkin models were almost same, whereas Langmuir parameter Q₀, for linear (1.60 to 9.434 μg g^-1) and non-linear (8.48 to 17.129 μg g^-1) models were quite different. For isotherms optimization different error functions such as sum of squares error (SSE), root mean square error (RMSE), Chi square error, hybrid fractional error (HYBRID) and average relative error (ARE) were calculated. Lowest error function values were obtained for Freundlich isotherm in all the soils except inceptisol (Kolkata) for which Langmuir isotherm gave the best fit. Statistical analysis using SAS 9.3 software and Tukey's HSD test revealed the significant effect (p < 0.001) of soil type on sorption. Sorption correlated positively with the organic carbon and clay contents of the soil.

Determination of pesticide residual levels in strawberry (Fragaria) by near-infrared spectroscopy

BACKGROUND

In this study, an infrared-based prediction method was developed for easy, fast and non-destructive detection of pesticide residue levels measured by reference analysis in strawberry (Fragaria × ananassa Duch, cv. Albion) samples using near-infrared spectroscopy and demonstrating its potential alternative or complementary use instead of traditional pesticide determination methods. Strawberries of Albion variety, which were supplied directly from greenhouses, were used as the study material. A total of 60 batch sample groups, each consisting of eight strawberries, was formed, and each group was treated with a commercial pesticide at different concentrations (26.7% boscalid + 6.7% pyraclostrobin) and varying residual levels were obtained in strawberry batches. The strawberry samples with pesticide residuals were used both to collect near-infrared spectra and to determine reference pesticide levels, applying QuEChERS (quick, easy, cheap, rugged, safe) extraction, followed by liquid chromatographic-mass spectrometric analysis.

RESULTS AND CONCLUSION

Partial least squares regression (PLSR) models were developed for boscalid and pyraclostrobin active substances. During model development, the samples were randomly divided into two groups as calibration (n = 48) and validation (n = 12) sets. A calibration model was developed for each active substance, and then the models were validated using cross-validation and external sets. Performance evaluation of the PLSR models was evaluated based on the residual predictive deviation (RPD) of each model. An RPD of 2.28 was obtained for boscalid, while it was 2.31 for pyraclostrobin. These results indicate that the developed models have reasonable predictive power. © 2019 Society of Chemical Industry.

Residue determination of pyraclostrobin, picoxystrobin and its metabolite in pepper fruit via UPLC-MS/MS under open field conditions

In this study, a new, high-efficiency and sensitive method was determined to simultaneous analyze the residue of pyraclostrobin, picoxystrobin and its metabolite BF-500-3 in pepper fruit using modified QuEChERS pretreatment combined with ultra performance liquid chromatography-tandem mass spectrometry. The clean-up steps of QuEChERS procedure were optimized using the chemometric tools. Models of stepwise regression and surface response demonstrated that the optimal sorbent mixtures were 40 mg nano-zirconia + 10 mg C₁₈ for pyraclostrobin and picoxystrobin and 30 mg nano-zirconia + 20 mg C₁₈ for BF-500-3. The optimized purification procedures provided satisfactory recoveries for all tested fungicides with rates between 91% and 107% and relative standard deviations between 3.7% and 9.6%. The limits of detection and quantification were in the range of 0.0360-0.272 μg/kg and 0.120-0.910 μg/kg. Based on this method, the dissipation of pyraclostrobin, picoxystrobin and its metabolite in pepper fruit were determined under field conditions. Pyraclostrobin and picoxystrobin degraded rapidly with half-lives of 5.53-7.02 and 5.97-7.82 days and 5.09 and 5.68 days in 2016 and 2017, respectively. The residue levels of BF-500-3 increased first and then decreased. The terminal residues of all fungicides were below the maximum residue limits (MRLs). This research can not only provide guidance for the reasonable usage of pyraclostrobin and picoxystrobin in agriculture but also give a reference for the Chinese government to establish the MRL for pyraclostrobin in pepper.

Dissipation and decontamination behavior of pre-mix formulation of tebuconazole and rifloxystrobin fungicides in okra

The present study was done to assess the dissipation behavior, decontamination, and half-life time of ready-mix formulation of trifloxystrobin (25% w/w) and tebuconazole (50% w/w) in okra and soil under the crop after foliar spray at fruiting stage. Samples of okra and soil were collected periodically, i.e., zero (2 h after spray), 1, 3, 5, 7, 10, 15, 20, and 25 days after third application at a 7-day interval. Residues of these fungicides were determined by gas liquid chromatography (GLC) equipped with electron capture detector (ECD) and gas chromatography-tandem mass spectrometry (GCMS-triple quadruple). The limits of quantification (LOQ) and detection (LOD) for both the fungicides were 0.01 and 0.003 mg kg^-1, respectively. Washing alone with faucet water was found successful in minimizing the residues. Soil was free from residual contamination at fifth day after spraying in case of both the fungicides and at both the doses.

Dynamic modeling of famoxadone and oxathiapiprolin residue on cucumber and Chinese cabbage based on tomato and lettuce archetypes

We analyzed the uptake and distribution of two pesticides (famoxadone and oxathiapiprolin) in herbaceous vegetables (cucumber and tomato) and leafy vegetables (Chinese cabbage and lettuce) to test the viability of applying existing archetypes in the dynamic plant uptake model dynamiCROP to modeling pesticide residue in other crops. Using field data and modeling, we showed that tomato was an unsuitable match for cucumber (R2 of 0.5325-0.6862) though lettuce was a good fit for Chinese cabbage (R2 of 0.8649-0.8862). We then used our cucumber data to add this as a new crop species archetype in dynamiCROP; further tests proved the accuracy of this approach (R2 of 0.8097-0.9152). In addition, we analyzed the distribution, uptake, and translocation of the two pesticides in cucumber and Chinese cabbage, using the model to better understand the mechanisms of pesticide residues over time and evaluate potential human exposure to pesticide residues from consumption of these crops. The fractions of famoxadone and oxathiapiprolin eventually ingested by humans based on our field trials ranged from 10-4 to 10-3 kg intake kg applied-1; that is, per kilogram of pesticide applied, humans would eventually consume less than one gram.

Application of different chromatographic techniques and chemometric analysis in authenticity testing of plant protection products containing azoxystrobin as an active substance

Azoxystrobin (methyl(2E)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy] phenyl}-3-methoxyacrylate) is an active ingredient used to protect crops against fungal diseases. The experience of the Polish control laboratory indicates relatively frequent cases of counterfeit plant protection products (PPPs) containing this active substance. The present study aimed to use chemometric methods to model chemical fingerprints obtained by different chromatographic techniques to verify the original formulation of PPPs containing the active substance azoxystrobin. The pesticides used in the study came from different sources (including stores and warehouses), were manufactured at a different time and came from different production batches. The results obtained with the HPLC-DAD and HS-GC-MS techniques were then modeled using principal component analysis (PCA) and soft independent modeling by class analogy (SIMCA) classifier. The proposed approach has been confirmed as useful for verifying the authenticity of PPPs and can be used in the routine control testing of SC pesticides containing azoxystrobin.

Soil fumigation alters adsorption and degradation behavior of pesticides in soil

Many crops are produced using soil fumigation and chemical pesticides to control soil-borne fungi and bacterial diseases, nematodes and weeds. Fumigation of soil, however, may alter its ability to adsorb, degrade and volatilize pesticides, which can then change the potential for pesticides to leach into groundwater. Soil adsorption kinetics, Freundlich isothermal adsorption and pesticide degradation techniques were used to determine the potential for pesticides to pollute groundwater in fumigated soil. The effect on soil pesticide adsorption in different types of chloropicrin (CP) fumigated soils was also examined. We observed that the equilibrium adsorption (q_e) decreased significantly at 24 h. Soil fumigation decreased the Freundlich K_f and K_foc values, and increased the Freundlich exponent ¹/_n values, for pesticides in fumigated Beijing soil. Soil fumigation influenced the K_f of pendimethalin, oxyfluorfen and abamectin the most, which themselves had a larger K_f in untreated soil. This indicated that the greater the soil pesticide adsorption the greater the influence of a fumigation treatment on that pesticide. The K_f was decreased more in the Heilongjiang and Beijing CP-fumigated soils that had high organic carbon content compared to Hunan soil. Fumigation of the soil with CP extended the half-life values of fosthiazate (from 34.3 to 43.1 days) and azoxystrobin (from 52.9 to 64.2 days), which increased their potential to leach into groundwater. Famers should minimize the quantity of some pesticides applied to fumigated soil, or apply some pesticides 60 days after fumigation, in order to avoid ground water pollution when crops are grown in fields or greenhouses.

Dissipation Dynamics and Dietary Risk Assessment of Kresoxim-Methyl Residue in Rice

Kresoxim-methyl is a high-efficiency and broad-spectrum fungicide used for the control of rice fungal diseases; however, its residues after application potentially threaten human health. Investigations on the dissipation of kresoxim-methyl residue in rice field systems and dietary risk assessment of kresoxim-methyl in humans are limited. The present study employed the QuEChERS-GC-MS/MS method for residue analysis of kresoxim-methyl in rice plants, brown rice, and rice husks. The samples were extracted with acetonitrile and purified by PSA, C₁₈ column, and GCB. The average recovery of the spiked target compounds in the three matrices was between 80.5% and 99.3%, and the RSD was between 2.1% and 7.1%. The accuracy and precision of the method is in accordance with the requirements of residue analysis methods. Dissipation dynamic testing of kresoxim-methyl in rice plants indicated a half-life within the range of 1.8–6.0 days, and a rapid dissipation rate was detected. Dietary intake risk assessment showed that the national estimated daily intake (NEDI) of kresoxim-methyl in various Chinese subpopulations was 0.022–0.054 μg/(kg bw·days), and the risk quotient (RQ) was 0.0000055–0.00014%. These findings indicate that the risk for chronic dietary intake of kresoxim-methyl in brown rice is relatively low. The present study provides information and theoretical basis for guiding the scientific use of kresoxim-methyl in rice fields and evaluating its dietary risk in brown rice.

Bitter gourd has the highest azoxystrobinon residue after open field application on four cucurbit vegetables

The goal of this study was to select a representative cucurbit vegetable crop that contained the highest residue levels of the pesticide azoxystrobinon. To do this, we used open field application of azoxystrobinon in four cucurbit crops (cucumber, zucchini, bitter gourd, and loofah) in Beijing, Shandong, and Anhui. Liquid chromatograph-mass spectrometry/mass spectrometry (LC-MS/MS) with selected reaction monitoring was used to determine azoxystrobinon levels in each of the selected cucurbit vegetables. The azoxystrobinon limit of detection was 0.005 mg kg-1 for all samples. Recoveries of azoxystrobinon ranged from 94.2% to 107.1% at spiked levels of 0.005-0.5 mg kg-1. In field trials, the half-life of azoxystrobinon in each of the four cucurbit crops was within the range of 1.4-3.1 d. Based on these results, we recommend that bitter gourd is selected as a representative cucurbit vegetable for future studies of azoxystrobinon. The obtained residual data were also assessed for their dietary risk and results indicated that there is no chronic dietary risk in any of the four, selected cucurbit vegetables. The recommended maximum residue limit (MRL) of azoxystrobinon in this subgroup was 0.2 mg/kg.

Degradation and metabolic profiling for benzene kresoxim-methyl using carbon-14 tracing

Benzene kresoxim-methyl (BKM) is an effective strobilurin fungicide for controlling fungal pathogens but limited information is available on its degradation and metabolism. This study explored the degradation and metabolic profiling for BKM in soils by carbon-14 tracing and HPLC-TOF-MS² analyzing. Results indicated that 88%-98% of ¹⁴C-BKM remained as parent or incomplete intermediates after 100 days. Three main radioactive metabolites (M1 to M3, ≥90%) and three subordinate radioactive metabolites (Ma to Mc, ≤2%) were observed, along with a non-radioactive metabolite M4. The main intermediates were further confirmed by self-synthesizing their authentic standards, and BKM was proposed to degrade via pathways including: 1) the oxidative cleavage of the acrylate double bond to give BKM-enol (M1); 2) the hydrolysis of the methyl ester to give BKM acid (M2); 3) the cleavage of M1 and M2 to yield Mc, which could be decarboxylated to give M3; and 4) the ether cleavage between aromatic rings to form M4. This study builds a solid metabolic profiling method for strobilurins and gives a deeper insight into the eventual fate of BKM by demonstrating its transformation pathways for the first time, which may also be beneficial for understanding the risks of other analogous strobilurins.

Parental diet affects embryogenesis of the great pond snail (Lymnaea stagnalis) exposed to cadmium, pyraclostrobin, and tributyltin

Diet quality has a strong impact on life-history traits, but it is not usually considered as a factor in toxicity tests. The purpose of the present study was to evaluate how diets differing in nutritional content affect sensitivity to cadmium, pyraclostrobin, and tributyltin in Lymnaea stagnalis offspring. Three groups were fed a different diet each: lettuce, high-caloric pellets, or a combination of both. Snails fed pellets and both diets had similar growth; however, snails fed lettuce showed lower growth until the fourth month. Egg masses were collected from adult snails fed each diet and exposed to 3 concentrations of either cadmium, pyraclostrobin, or tributyltin. We quantified time to hatch, hatching success, and the developmental stages of embryos. We measured fecundity in adults and total lipids, carbohydrates, and proteins in adult snails and egg masses. Adult snails fed different diets produced a similar number of egg masses, but the number of eggs per egg mass in snails fed pellets was lower than for snails fed the other 2 diets. We found that adult snails fed pellets had a higher lipid content compared to snails fed the other 2 diets. However, egg masses from parental snails fed pellets did not hatch, including those from the controls. Interestingly, egg masses exposed to the lowest concentration of tributyltin had low hatching success. These observations on offspring performance suggest that there are important diet effects that can strongly influence responses that could be diet- and chemical-dependent. Environ Toxicol Chem 2018;37:2428-2438. © 2018 SETAC.

Assessment of boscalid and pyraclostrobin disappearance and behavior following application of effective microorganisms on apples

The aim of this study is to assess the disappearance of boscalid (IUPAC name: 2-chloro-N-[2-(4-chlorophenyl)phenyl]pyridine-3-carboxamide) and pyraclostrobin (IUPAC name: methyl N-[2-[[1-(4-chlorophenyl)pyrazol-3-yl]oxymethyl]phenyl]-N-methoxycarbamate) residues in apple fruit, and to verify whether an organic fertilizer enriched with strains of antagonistic microorganisms can reduce pesticide residue levels. Field trials were conducted in a commercial orchard on apples of the Gloster variety, during 21 days after the treatment with Bellis 38 WG and the subsequent application of Zumba Plant formulation containing Bacillus spp., Trichoderma spp. and Glomus spp. In control samples, the decrease rate of boscalid and pyraclostrobin residue levels followed an exponential function, described by formulae R_t = 0.2824e^-0.071t and R_t = 0.1176e^-0.060t, with the coefficient of determination of r² = 0.8692 and r² = 0.9268, respectively. These levels dropped to half (t_1/2) of their initial values after 9.8 and 11.5 days, respectively. The treatment with Zumba Plant resulted in a reduction in boscalid and pyraclostrobin residue levels by 52% and 41%, respectively. The results of this study are of importance for horticulture sciences and for producers of apples using plant protection products (PPPs).

Whole body dosimetry and risk assessment of agricultural operator exposure to the fungicide kresoxim-methyl in apple orchards

This study examined dermal and inhalation exposure of agricultural operators to kresoxim-methyl during pesticide mixing/loading and speed sprayer application (10 replicates, each of 3000 L of spray suspension) in an apple orchard and performed risk assessment. For the whole body dosimetry (WBD) exposure protocol, outer clothing, inner clothing, gauze, and nitrile gloves were examined to measure dermal exposure. In contrast, an IOM (institute of occupational medicine) sampler with a glass fiber filter was used to measure inhalation exposure. Analytical method accuracy in the exposure matrices was evaluated by a field recovery study. The dermal and inhalation exposure amounts for mixing/loading were 9.7 mg [0.002% of the total mixed/loaded active ingredient (a.i.)] and 1.2 µg (1.7 × 10^-6% of the total mixed/loaded a.i.), respectively. The body parts more exposed were the forearms (35.5%), chest & stomach (30.2%), and hands (17.9%). During application, the dermal and inhalation exposure amounts were 66.5 mg (0.009% of the total applied a.i) and 34.8 µg (4.6 × 10^-5% of the total applied a.i.), respectively. The shins (18.5%) and chest & stomach (16.0%) were exposed to higher proportion of pesticide, followed by the thighs (15.8%) and back (14.7%). Comparing the exposure pattern as assessed by the WBD method in the present study with the patch method as in our previous study, the ADE (actual dermal exposure) as measured by the WBD method was 25 times less than that measured by the patch method. The daily exposure amounts of ADE and AIE (actual inhalation exposure) for mixing/loading were 711.8 µg/day and 4.3 µg/day, respectively, whereas the amounts of ADE and AIE for application were 1825.8 µg/day and 116.1 µg/day. In risk assessment of the mixing/loading and application scenarios, the AOEL (acceptable operator exposure level) of kresoxim-methyl was used as the reference dose to show that the RI (risk index) was much lower than 1, indicating that agricultural operators are at low risk of exposure to kresoxim-methyl.

Transfer of the Active Ingredients of Some Plant Protection Products from Raspberry Plants to Beehives

Plant protection products (PPPs) have been found increasingly in the environment. They pose a huge threat to bees, contributing to honeybee colony losses and consequently to enormous economic losses. Therefore, this field investigation was designed to determine whether their active ingredients (AIs) were transferred from raspberry plants to beehives located in the immediate neighbourhood of the crop and to what extent they were transferred. Every week for 2 months, samples of soil, raspberry leaves, flowers and fruits, worker bees, honeybee brood, and honey were collected and analysed for the presence of propyzamide, chlorpyrifos, iprodione, pyraclostrobin, boscalid, cypermethrin, difenoconazole, azoxystrobin, and pyrimethanil residues. Five of these substances were found in the worker bee bodies. Chlorpyrifos, applied to only the soil through the irrigation system, also was detected in the brood. A small amount of boscalid was noted in the honey, but its residues did not exceed the maximum residue level. For chlorpyrifos, boscalid, and pyrimethanil, a positive correlation between the occurrence of PPPs in the crops and the beehives was found. Statistical methods confirmed that the application of PPPs on a raspberry plantation, as an example of nectar-secreting plants, was linked to the transfer of their AIs to beehives.

Matrix Effect Evaluation and Method Validation of Azoxystrobin and Difenoconazole Residues in Red Flesh Dragon Fruit (Hylocereus polyrhizus) Matrices Using QuEChERS Sample Preparation Methods Followed by LC-MS/MS Determination

Production of red flesh dragon fruit (Hylocereus polyrhizus) was hampered by Colletotrichum sp. Pre-harvest application of azoxystrobin and difenoconazole mixture is recommended, therefore, a selective and sensitive multi residues analytical method is required in monitoring and evaluating the commodity's safety. LC-MS/MS is a well-established analytical technique for qualitative and quantitative determination in complex matrices. However, this method is hurdled by co-eluted coextractives interferences. This work evaluated the pH effect of acetate buffered and citrate buffered QuEChERS sample preparation in their effectiveness of matrix effect reduction. Citrate buffered QuEChERS proved to produce clean final extract with relative matrix effect 0.4%-0.7%. Method validation of the selected sample preparation followed by LC-MS/MS for whole dragon fruit, flesh and peel matrices fortified at 0.005, 0.01, 0.1 and 1 g/g showed recoveries 75%-119%, intermediate repeatability 2%-14%. The expanded uncertainties were 7%-48%. Based on the international acceptance criteria, this method is valid.

Evaluation of Self-Propelled High-Energy Ultrasonic Atomizer on Azoxystrobin and Tebuconazole Application in Sunlit Greenhouse Tomatoes

In this study, a self-propelled high-energy ultrasonic atomizer was evaluated in terms of deposition on the canopy, the loss to the ground, and fungicide residues in cherry tomato and tomato. Artificial collectors fixed to the upper side and underside of the leaves at different depths and heights were used to collect the depositions. A reliable analytical method for determination of azoxystrobin and tebuconazole in artificial collectors and residue samples was developed by using liquid chromatography triple-quadrupole mass spectrometry. The results showed that the atomizer distributed the droplets evenly throughout the greenhouse with good uniformity (CVs below 39%). The ratio of depositions on the internal and external sides was 66⁻83%, and the ratio of depositions on the underside and upper side was 39⁻50%. There were no significant differences in depositions between two different height crops. The residues of azoxystrobin and tebuconazole in tomato and cherry tomato fruits were far below the maximum residue limits at harvest time. In general, self-propelled high-energy ultrasonic atomizer used in a greenhouse could increase the depositions, especially on the underside and internal side of the canopies, and lead to a reduction of operator exposure risk.

Simultaneous determination and risk assessment of metalaxyl and azoxystrobin in potato by liquid chromatography with tandem mass spectrometry

A liquid chromatography with tandem mass spectrometry method was developed and validated to simultaneously determine metalaxyl and azoxystrobin in soil, potato, and potato foliage samples. The samples were extracted by 20 mL of acetonitrile and purified with dispersive solid-phase extraction using octadecyl silane as sorbent. The method showed good linearity (determination coefficients ≥ 0.9926) for metalaxyl (2.5-500 ng/mL) and azoxystrobin (5-1000 ng/mL). The limits of detection and quantification for both fungicides were 1.5-20 μg/kg. The average recoveries in soil, potato, and potato foliage were 83.07-92.87% for metalaxyl and 82.71-98.53% for azoxystrobin. The intra- and inter-day relative standard deviations were all less than 9%. The method was successfully applied on the residual analysis of metalaxyl and azoxystrobin in field trial samples. The results showed that the concentrations of metalaxyl and azoxystrobin in potato samples collected from Guizhou and Hunan were below 50 and 100 μg/kg (maximum residue limit set by China), respectively, at 5 days after the last application. When following the recommended application manual, metalaxyl and azoxystrobin do not present health concerns to the population because the risk quotients are far below 100%. All the above data could help and promote the safe and proper use of metalaxyl and azoxystrobin in potato.

Grab and passive sampling applied to pesticide analysis in the São Lourenço river headwater in Campo Verde - MT, Brazil

In this study, the quality of surface water in the headwaters of São Lourenço River in Mato Grosso, Brazil, was evaluated in relation to contamination by pesticides. For this purpose, samples were collected between December 2015 and June 2016 by grab sampling and by passive sampling using an integrative polar organic compound sampler installed in the field during four 14-day cycles between March and June 2016. The analyses were performed by gas chromatography (CG/MS) and by liquid chromatography (UPLC-MS/MS). The results showed the detection of two pesticides (atrazine and pyraclostrobin) of the five analyzed by passive sampling and eight active principles among the 20 analyzed (malathion, diuron, carbofuran, carbendazim, trifluralin, imidacloprid, metolachlor, and acetamiprid) by grab sampling. The detection of 10 pesticides, even almost a decade after the beginning of a recovery process of the ciliary forest, confirms the headwaters' vulnerability to these contaminants and passive sampling proved to be an important tool in capturing small concentrations of pesticides constituting an interesting complement to grab sampling.

Diet quality affects chemical tolerance in the freshwater snail Lymnaea stagnalis

Organisms generally select high-quality diets to obtain maximal energy while devoting the least amount of time and energy. Diets, however, can vary in natural systems. In ecotoxicological testing, the effect of diet type on organismal responses to toxicants has not been explored despite the potential for dietary effects to influence toxicological endpoints. We first evaluated diet quality using growth rate and sensitivity to the fungicide pyraclostrobin of Lymnaea stagnalis fed lettuce (common laboratory diet), turtle pellets (high nutrient composition), and a combination diet of both food items. We also measured the macronutrient content of snails raised on the multiple diets to determine how diet may have impacted energy allocation patterns. Finally, we evaluated whether snails discernibly preferred a particular diet. Snails fed high-nutrient and combination diets grew larger overall than snails fed a lettuce-only diet. Snails fed the high-nutrient and combination diets, both juvenile and adult, were significantly more tolerant to pyraclostrobin than snails fed lettuce. When measured for macronutrient content, snails raised on high-nutrient and combination diets had significantly higher carbohydrate content than snails fed lettuce. Despite the strong effects of diet type, snails did not exhibit a clear diet choice in preference trials. Dietary composition clearly influences growth rate, sensitivity, and macronutrient content of Lymnaea stagnalis. These results suggest that the nutritional environment has potentially strong impacts on toxicant sensitivity. Environ Toxicol Chem 2018;37:1158-1167. © 2017 SETAC.

Dissipation behaviour, residue distribution and dietary risk assessment of tetraconazole and kresoxim-methyl in greenhouse strawberry via RRLC-QqQ-MS/MS technique

20% commercial suspension emulsion (SE) of (8% tetraconazole + 12% kresoxim-methyl), as a pre-registered product in China, was firstly investigated under Chinese greenhouse-field conditions. A MWCNTs-based QuEChERS method for simultaneous determination of tetraconazole and kresoxim-methyl in strawberry was developed and validated via RRLC-QqQ-MS/MS. On basis of this method, the dissipation behaviours, residue distributions and dietary risk probability of these fungicides in strawberry were further investigated for food safety. The dissipations of tetraconazole and kresoxim-methyl followed first-order kinetics with the half-lives of 8.0-18.2 days. The highest residues (HRs) of these fungicides in the supervised trials at the pre-harvest interval (PHI, 3 days) were below 0.8970mgkg^-1. The total national estimated daily intake (NEDI) of tetraconazole and kresoxim-methy in strawberry at the PHI 3day was 0.2784mg and 0.4031mg, respectively, based on Chinese dietary pattern and terminal residue distributions under good agricultural practices (GAP) conditions. The risk quotients (RQs) of tetraconazole and kresoxim-methy at PHI 3 days were below 82.7% and 1.6%, respectively, showing that the evaluated strawberry exhibited an acceptably low dietary risk to consumers. The current study could not only guide reasonable usage of the formulation, but also facilitate the setting of maximum residue limits (MRLs) of tetraconazole in strawberry.

Comparison of a new air-assisted sprayer and two conventional sprayers in terms of deposition, loss to the soil and residue of azoxystrobin and tebuconazole applied to sunlit greenhouse tomato and field cucumber

BACKGROUND

Plant protection products (PPPs) are applied in China and many other developing countries with knapsack sprayers at high volumes with coarse spray quality, resulting in a high percentage of pesticide losses. In this study, a new air-assisted electric knapsack sprayer and two conventional knapsack sprayers were evaluated in terms of pesticide deposition, residues and loss into the soil. Artificial targets fixed to the upper side and underside of the leaf surface in six zones (at two depths and three heights) were used to collect the deposition, which were analyzed by liquid chromatography triple-quadrupole mass spectrometry.

RESULTS

The air-assisted electric knapsack sprayer produced more deposition and better penetrability and uniformity than the two traditional spraying methods. In particular, the air-assisted electric knapsack sprayer reduced pesticide losses to the soil by roughly 37% to 75% and deposited 1.18 and 1.24 times more pesticide than the manual air-pressure and battery-powered knapsack sprayers, respectively. The residues of azoxystrobin and tebuconazole in tomato and cucumber were below the maximum residue limits (MRLs).

CONCLUSION

In general, use of the the air-assisted electric knapsack sprayer in tomato and cucumber crops could improve the effectiveness of PPPs, reduce the risk of contamination and protect food safety. © 2017 Society of Chemical Industry.

The transfer of active ingredients of insecticides and fungicides from an orchard to beehives

This investigation was undertaken to determine whether active ingredients (AIs) of currently recommended plant protection products (PPPs) could be transferred to beehives from apple and pear trees. A field trial was carried out with apple trees of Ligol and Idared variety, and pear trees of Conference variety. For pest and diseases control of fungal origin, recommended PPPs were applied. Samples of flowers from the above-mentioned varieties of fruit trees, of bees, brood and honey from beehives located in their direct neighborhood were collected regularly and analyzed for the presence of lambda-cyhalothrin (an insecticide) and cyprodinil, captan, fluopyram, kresoxim-methyl, penthiopyrad and trifloxystrobin (fungicides). In samples of flowers of Ligol variety, fluopyram residues (on average 0.621 µg single flower^-1) were at the highest levels, whereas in samples of pear flowers of Conference variety, and in flowers of Idared variety, captan residues (on average, respectively, 0.705 and 165.7 µg single flower^-1). In samples of bees and honey, residues of five AIs were detected, and in brood six AIs, whereby in each case captan residues prevailed, respectively, up to 585.2, 51.52 and 126.5 µg kg^-1 bees and honey. In the honey, significantly larger residues of captan were found out than maximum residue level (MRL) for this AI - 103.04% MRL. In the case of any AI, the daily intake did not exceed 0.002% acceptable daily intake (ADI).

Enantioselective degradation of Myclobutanil and Famoxadone in grape

The enantioselective degradation of myclobutanil and famoxadone enantiomers in grape under open field was investigated in this study. The absolute configuration of myclobutanil and famoxadone enantiomers was determined by the combination of experimental electronic circular dichroism (ECD) and calculated ECD spectra. The enantiomers residues of myclobutanil and famoxadone in grape were measured by sensitive high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS). The linearity, precision, accuracy, matrix effect, and stability were assessed. And the limit of quantification (LOQ) for each enantiomer of myclobutanil and famoxadone in grape was evaluated to be 1.5 and 2 μg kg^-1. The myclobutanil and famoxadone showed the enantioselective degradation in grape, and the enantioselectivity of degradation for myclobutanil was more pronounced than that for famoxadone. The half-lives were 13.1 days and 25.7 days for S-(+)-myclobutanil and R-(-)-myclobutanil in grape, separately. The half-life of S-(+)-famoxadone was 31.5 days slightly shorter than that of R-(-)-famoxadone with half-life being 38.5 days in grape. The probable reasons for the enantioselective degradation behavior of these two fungicides were also discussed. The results in the article might provide a reference to better assess the risks of myclobutanil and famoxadone enantiomers in grapes to human and environment. Graphical abstract The enantioselective analysis of myclobutanil and famoxadone in grape.

Liquid chromatography-tandem mass spectrometry method for simultaneous quantification of azoxystrobin and its metabolites, azoxystrobin free acid and 2-hydroxybenzonitrile, in greenhouse-grown lettuce

Lettuce is an important part of the diet in Europe. The permitted levels of pesticides in lettuce are strictly regulated and there is growing urge among food safety authorities to analyse pesticide metabolites as well. Azoxystrobin is one of pesticides that is frequently detected in lettuce. Although there are several analytical methods for the determination of azoxystrobin in lettuce, a sensitive method for the determination of its metabolites in lettuce is lacking. This study aimed at developing an extraction and LC-MS/MS method for the simultaneous determination of azoxystrobin, and its metabolites azoxystrobin free acid and 2-hydroxybenzonitrile in lettuce. Accelerated solvent extraction, QuEChERS extraction, and shaking extraction were compared using various solvents. The final method consisted of shaking freeze-dried sample in 0.1% formic acid in 80% aqueous acetonitrile. The selected method was validated by spiking each analyte at 125 ng/g and 500 ng/g. The method resulted in acceptable recovery for 2-hydroxybenzonitrile, azoxystrobin free acid, and azoxystrobin, with a RSD of <10%. The matrix-matched calibration curve for each analyte was linear over the range of quantification, with a correlation coefficient ≥0.98. The method was sensitive for the determination of 2-hydroxybenzonitrile, azoxystrobin free acid, and azoxystrobin, with limits of quantification of 0.36, 0.48, and 0.68 ng/g dry weight, respectively. The method was successfully applied to quantify 2-hydroxybenzonitrile, azoxystrobin free acid, and azoxystrobin in greenhouse-grown lettuce.

Ambient mass spectrometry: Direct analysis of dimethoate, tebuconazole, and trifloxystrobin on olive and vine leaves by desorption electrospray ionization interface

A new field of application for a relatively new mass-spectrometric interface such as desorption electrospray ionization was evaluated. For this purpose, its behavior was tested versus quantitative analysis of dimethoate, trifloxystrobin, and tebuconazole directly on olive and vine leaves surface. The goal was workers exposure assessment during field re-entry operations since evidence suggests an association between chronic occupational exposure to some agrochemicals and severe adverse effects. Desorption electrospray ionization gave good response working in positive ionization mode, while numerous test were necessary for the choice of a unique blend of spray solvents suitable for all 3 substances. The best compromise, in terms of signal to noise ratios, was obtained with the CH₃ OH/H₂ O (80:20) mixture. The obvious difficulties related to the impossibility to use the internal standard were overcome through an accurate validation. Limits of detection and quantitation, dynamic ranges, matrix effects, and intraday precisions were calculated, and a small monitoring campaign was arranged to test method applicability and to evaluate potential dermal exposure. This protocol was developed in work safety field, but after a brief investigation, it was find to be suitable also for food residue evaluation.

Influence of commercial formulation on leaching of four pesticides through soil

Studies with small soil columns (2cm i.d.×5.4cm depth) compared leaching of four pesticides added either as technical material or as commercial formulations. Pesticides were selected to give a gradient of solubility in water between 7 and 93mgL^-1, comprising azoxystrobin (emulsifiable concentrate, EC, and suspension concentrate, SC), cyproconazole (SC), propyzamide (SC) and triadimenol (EC). Columns of sandy loam soil were leached with 6 pore volumes of 0.01M CaCl₂ either 1 or 7days after treatment. Separate experiments evaluated leaching of triadimenol to full breakthrough following addition of 18 pore volumes of 0.01M CaCl₂. The mass of pesticide leached from columns treated with commercial formulation was significantly larger than that from columns treated with technical material for all compounds studied and for both leaching intervals (two-sided t-tests, p<0.001). This difference was conserved when triadimenol was leached to full breakthrough with 79±1.2 and 61±3.1% of applied triadimenol leached from columns treated with formulated and technical material, respectively. There were highly significant effects of formulation for all pesticides (two-way ANOVA, p<0.001), whereas leaching interval was only significant for azoxystrobin EC formulation and cyproconazole (p<0.001 and 0.021, respectively) with greater leaching when irrigation commenced 1day after treatment. Leaching of azoxystrobin increased in the order technical material (6.0% of applied pesticide)<SC formulation (8.5-9.1% of applied)<EC formulation (15.8-21.0% of applied). The relative difference between leaching of formulated and technical pesticide increased with pesticide solubility in water, increasing from a factor of 1.4 for the SC formulation of azoystrobin to 4.3 for the SC formulation of triadimenol. Experimental systems differ markedly from field conditions (small columns with intense irrigation). Nevertheless, results indicate the need to consider further the influence of co-formulants in pesticide formulations on behaviour of the active ingredient in soil.

Persistence in and Release of 2,4-D and Azoxystrobin from Turfgrass Clippings

Research has shown that pesticide residue in clippings from previously treated turfgrass may become bioavailable as grass decomposes, adversely affecting off-target organisms. We conducted a field study to quantify 2,4-D (2,4-dichlorophenoxyacetic acid) and azoxystrobin (methyl(E)-2-{2[6-(2-cyanophenoxy)pyrmidin-4-yloxy]phenyl}-3-methoxyacrylate) residues in turfgrass clippings collected from hybrid bermudagrass [ (L.) Pers. × Burtt-Davy], tall fescue [ (Schreb.) S.J. Darbyshire], and zoysiagrass ( Steud.). A subsequent greenhouse experiment was conducted to measure pesticide release from clippings into water. 2,4-D (1.6 kg a.i. ha) and azoxystrobin (0.6 kg a.i. ha) were applied to field plots at 32, 16, 8, 4, 2, 1, or 0 d before collection of the clippings. Clippings were collected from each experimental unit to quantify pesticide release from clippings into water. Both 2,4-D and azoxystrobin were detected when turfgrass was treated over the 32-d experimental period, suggesting that clipping management should be implemented for an extended period of time after application. Pesticide residue was detected in all water samples collected, confirming 2,4-D and azoxystrobin release from turfgrass clippings; however, pesticide release varied between compounds. Two days after clippings were incorporated in water, 39 and 10% of 2,4-D and azoxystrobin were released from clippings, respectively. Our research supports the currently recommended practice of returning clippings to the turfgrass stand when mowing because removal of 2,4-D and azoxystrobin in clippings may reduce pest control and cause adverse off-target impacts.